1. Field of the Invention
The present invention relates to a method of performing a uniform illumination pattern in a back-light plate. More specifically, the present invention relates to a method of performing a uniform illumination pattern in a back-light plate by pressing.
2. Description of the Prior Art
The inner light source of a scanner or a liquid crystal display (LCD) comprises a fluorescent tube and a back-light plate to form a back-light source, in order to scan a transparent document or to illuminate an LCD panel. Because the fluorescent tube is placed on one incident side of the back-light plate, the light emitted from the back-light plate is not uniformly distributed over the entire back-light plate. Light is especially brighter in the area near the incident side of the back-light plate. In order to solve the problem of non-uniform illumination, the prior art teaches to make plural spots on the back-light plate. The purpose of these spots is to reflect the light from the incident side of the back-light plate, so the light emitting from the illuminating face can be uniform.
Please refer to FIG. 1. FIG. 1 depicts a top view of a back-light plate 10 of the prior art. The prior art back-light plate 10 is a substantially flat and transparent plate structure, which comprises two parallel illuminating faces, and a substantially linear tube 12 is placed on one incident side of the back light plate 10. There are plural spots 16 on one illuminating face 14 of the back-light plate 10. These spots form a uniform illumination pattern. The farther the spot is away from the tube 12, the bigger the spot is, and the distance between the spot and its adjacent spots is shorter. On the contrary, the nearer the spot is from the tube 12, the smaller the spot is, and the distance between the adjacent spots is longer. When a visible light illuminating from the tube 12 incidents into the back-light plate 10 from the incident side, the plural spots of various sizes and different spacing distances make the emitting light uniformly distributed over the entire back-light plate 10. The prior art methods of performing the uniform illumination pattern on a back-light plate are mainly divided into two kinds: the printing method and the injection molding method. The printing method prints the spots 16 on the hard acrylic resin plate by hand. High cost and unstable printing quality are the main problems of this method. The printing quality is not easily under control. For example, the ink spreads when it is too much and it becomes non-uniform when the ink is not enough. Besides, this method cannot achieve the purpose of total reflection because ink tends to absorb light. As to the injection molding method, a pattern mold according to the design of uniform illumination pattern is needed. It is not only expensive, but also leads to inconvenience when molds of different pattern design are to be fabricated. Due to the aforementioned problems, there is indeed an urgent need to develop a new method to perform a uniform illumination pattern on a back-light plate in order to reduce the cost of materials and manufacturing, and hereby enhance competence of the manufacturer.
It is therefore a primary objective of this invention to provide a method of performing a uniform illumination pattern in a back-light plate utilizing a press. The present invention not only avoids the drawbacks in the prior arts, but also reduce the cost of materials, manufacturing, and their assembly.
The present invention provides a method utilizing a press with a plurality of protruding elements to press an illuminating face of the back-light plate so as to form a plurality of recesses with predetermined depths thereon. These recesses can work as a uniform illumination pattern on the back-light plate. When the visible light emitting into the back-light plate, the plurality of recesses on the illuminating face would make the emitting visible light illuminate uniformly on the back-light plate so as to achieve its originally intended purpose.